rAH75 



' BUBJECT TO REVISION. 

[TRANSACTIONS OF THE AMERICAN INSTITUTE OF MINING ENGINEERS.1 



The Need of Standard Specifications for Gray-Iron 
Castings. 

BY HENRY SOUTHER, HARTFORD, CONN. 
Atlantic City Meeting, February, 1904.) 

It is generally admitted that a good practical and commercial 
•set of specifications for use by the many cast-iron purchasers 
does not exist. A few good sets are in the hands of large buy- 
ers, but even these are very different, contradictory, and not 
intended to cover a wide range of product. Most of these sets 
have been written to cover one industry only. 

It is strange that purchasers of cast-iron have not looked into 
this question long ago and demanded good, uniform cast-iron. 

Probably cast-iron has been discarded from many uses be- 
cause of its failure in some few instances, even though the fail- 
ure was due to ignorance of the quality of the iron, or perhaps 
to abnormally bad iron. It is not too extreme to say that some 
-consider all gray-iron from a given foundry alike and uniform, 
especially if they know it is made from certain well-known 
brands of iron. It is likely that with standard specifications 
and the increase of knowledge necessary to meet these condi- 
tions, the use of gray-iron castings will enter into fresh fields 
because of the certainty of quality. This was the case when 
steel replaced wrought-iron, for the reason that it was made of 
a uniformly good quality and was thoroughly reliable. 

The foundryman, therefore, should welcome any good com- 
mercial steps taken in the direction of securing standard specifi- 
cations for cast-iron. 

Uniformity of product in soft steel is comparatively easy to 
bring about, and yet the most rigid s])ecifiia':ions a •€■ \^' com- 
mon use by the purchasers of this material. 



h-j:^i- 



T 



k^^^^ 




"A STANDARD SPECIFICATIONS FOR GRAY-IRON CASTINGS. 

Uniformity of product in cast-iron is not easy to attain be- 
cause of the greater quantity of impurities in it, yet specifica- 
tions for soft steel are common while for cast-iron they are rare.. 

In steel, only carbon, phosphorus and sulphur are of prime 
importance, manganese, silicon and copper being secondary, 
and all of these impurities exist in very small percentages. 

In cast-iron, however, silicon, sulphur, carbon and phospho- 
rus are of vital importance and are present in comparatively 
large percentages. Furthermore, each impurity is capable of 
notably altering the quality of the metal. Manganese also as 
a secondary element is to be intelligently regulated to advan- 
tage. 

Yet cast-iron with the greatest possible variation in composi- 
tion is neither watched, inspected nor tested in spite of the 
immense differences possible, while soft steel which may vary 
but little in comparison is submitted to a careful examination 
before it is accepted. This circumstance is not due to the fact 
that cast-iron is *not used at critical points either, because it is 
used in making columns, the breaking of which may wreck a 
building, as cast-iron enters into the manufacture of high- 
pressure valves and fittings that may wreck a boiler or an 
hydraulic system, as well as into many other important uses. 

Not only is cast-iron subject to chemical and physical differ- 
ences under normal conditions, but, like most cast metals, it is 
liable to have bad internal flaws and latent defects not possible 
to detect by any other means than a test to destruction. In 
many cases these defects are the indirect results of bad chemi- 
cal conditions, for example, a high sulphur percentage, and it 
is for this reason, if for no other, that a limit to the sulphur- 
content should have a place in cast-iron specifications. 

Process of Manufacture. 
In certain grades of gray-iron an unusual strength is de- 
manded, and in many instances it is convenient to make this 
grade in a reverberatory or air-furnace. Under the specifica- 
tions submitted, either method is permitted, each being believed 
to be good, but, unless otherwise specified, the cupola-furnace 
will be used. It is known that some founders produce all 
grades *of feasting .:;njthG cupQliJi-fiirnace successfully, by the in- 
telligeiit'use of-'both'irOTi and fuel. 



standard specifications for gray-iron castings. 6 

Chemical Properties. 

It is believed that light iron-castings should be more free from 
sulphur than heavy ones, because the presence of sulphur in- 
duces chill, shrinkage and such flaws as are grouped under the 
broad head of " dirty iron." All of these defects are more serious 
in light work than in heavy ; the chill, because it is possible in 
thin iron and not in thick iron, the latter containing so much 
heat as to cause it to anneal itself in cooling ; shrinkage, be- 
cause light castings chill quickly, form a small, close grain and 
shrink more in consequence, whereas heavy castings cool slowly, 
form large, open grain and shrink much less ; and flaws, because 
a flaw of a given size forms a much more serious defect in a 
light casting than in a heavy one. It is a fact that flaws in- 
duced by the presence of sulphur do not decrease in proportion 
to the decrease in the bulk of a casting, and it is common to 
find shot-holes in small castings of about the same size as those 
in much larger castings. 

The sulphur-limits placed in these specifications are within 
the commercial reach of any well-regulated foundry, and neces- 
sitate no extra cost. The low sulphur-limit for heavy castings 
has been objected to as unnecessarily low, but it is on the safe 
side and is an insurance against bad flaws and should be re- 
tained, for the reason that it does not increase the cost of the 
iron. 

Cast-iron with high sulphur-content is sometimes stronger 
than with low, because the grain in the former instance is 
closer, a condition which always tends to increase the strength ; 
but of what use is the extra strength if at some vital point in 
the casting flaws exist as a result of high sulphur-content, that 
weaken it and far more than offset the extra strength of the 
sound parts of the casting. 

Even if it is assumed that a test-bar representing a cylinder 
does show unusual strength and is of high sulphur-content and 
sound at the point of rupture, the casting itself may contain 
■enough shot- and blow-holes to cause failure. 

A high sulphur-content is a menace in any casting, whether 
it can be detected physically or not, and this impurity should 
be excluded as far as possible commercially. 



4 standard specifications for gray-iron castings. 

Physical Properties. 

The figures given in Table I. have been taken from as many 
tests as was possible to accumulate in the short time available 
after determining the dimensions of the test-specimen. All 
kinds of iron are not represented, but those that are given 
show very encouraging results. 

I was not able to get reliable information in all cases. The 
bars are from six foundries, making products very varied in 
character. 

From the same foundries the results of testing the inch- 
square bars selected at random from recent tests are given in 
Table 11. for comparison, being tests made under exactly sim- 
ilar conditions. N'os. 12,761 and 12,762 were from the same 
ladle of metal as I^[os. 12,759 and 12,760. 

The theoretical ratio of strength of the inch-square bar in 
common use as compared with the arbitration bar is about 
0.8 to 1, or, to be exact, 0.867; that is, the inch-square bar is 
about 80 per cent as strong as the IJ-in. round bar, all things 
being equal. The results of the few tests made in both shapes 
from the same run is close to this, as is shown in Tables I. 
and II. Actual results do not follow the theory exactly for 
the reason that the greater volume of the arbitration bar re- 
sults in its being softer, all other things being equal. There 
is also a lesser proportion of chilled metal in the round bar. 

The worst enemy of the cast-iron test-specimen is the physi- 
cal defect or flaw. Fewer of the round test-bars contain flaws- 
than of the square. It is apparent that the sharp corners by 
capillarity or similar influences attract rising bubbles of gas and 
entrap them in the quicker cooling metal contained in the cor- 
ners. This efiect alone places the round bar superior to the 
square as a fair representative of a cast. 

The figures given in Table I. show that the transverse 
strength-limits are placed so low that no difficulty should be- 
experienced in filling the requirements. 

After obtaining more data it may be found that higher 
strength-limits are possible and advisable. With the ones 
given, however, uniformity and good quality are insured, 
which is the main object to be desired at present. 

No upper-strength limit has been placed as this factor is con- 



Table I. — Results Obtained from Tests Made with Arbitration 

Test-Bars. 



No. of 
Specimen. 


Deflection 

in 12 

Inches. 


Strength. 


Phosphorus. 


Manga- 
nese. 


Sulphur. 


Silicon. 




Inches. 


Pounds Per 
Sq. In. 


Per Cent. 


Per Cent. 


Per Cent. 


Per Cent. 


12,1741 
12,175 / 


0.15) 
0.12) 


3,500^ 
3.600 i 


0.630 


0.30 


0.128 


1.819 


12.266 \ 

12.267 1 


0.09) 
0.07 f 


3,500) (Cast 
3,200/ fi 


ni-t ^-^^^ 


0.60 


0.144 


2.383 


12.269 1 

12.270 r 


0.07) 

0.08/ 


3,200) 
3,200/ 


0.653 


0.18 


0.104 


2.040 


12.343 \ 

12.344 1 


0.13) 

0.11 ; 


:'5,300) 
3,000 J 


0.520 


0.36 


0.099 


1.683 


12,345 \ 
12,346/ 


0.12 \ 
0.13) 


3,200\ 
3,000 j 


(These bars 


had fins.) 





1.584 


12.429 \ 

12.430 J 


0.10) 
0.08 / 


2,800 \ 
2,800 i 


0.534 


0.36 


0.098 


1.725 


12.431 X 

12.432 ( 


0.10) 
0.1(»/ 


3,500) 
3,100 J 


(All cast 


with fins.) 




1.810 





12,433) 
12,434 / 


0.13) 
0.11 i 


3,500) 
3,800/ 


0.340 


0.30 


0.113 


1.340 


12.435 \ 

12.436 / 


0.11) 
0.12/ 


3,500) 
3,400/ 


0.364 


0.28 


0.101 


1.678 


12.480 \ 

12.481 i 


0.14) 
0.12 J 


3,600) 
3,800/ 


0.681 


0.30 


0.105 


2.092 


12,546) 
12,547 / 


0.07) 
0.11/ 


3,2U0) 
3,400 / 


0.562 


0.32 


0.095 


r 1.899 
11.848 


12,551 ) 
12,552 / 
12,553) 
12,554 / 


0.09) 
0.09 J 


2,700) 
3,000/ 


0.326 


0.38 


0.088 


1.565 


0.06) 
0.09/ 


2,600) 
3,100/ 


0.377 


0.36 


0.097 


1.631 


12,638 


Lost. 


3,500 


0.536 


0.42 


0.088 


1.974 


12,639 


0.10 


4,100 


0.687 


0.24 


0.089 


1.960 


12,673 ) 
12,674/ 


0.10) 

0.13 r 


2,900) 
3,550/ 


0.580 


0.34 


0.124 


1.706 


12,675) 
; 12,676/ 


0.11) 
0.11/ 


3,500) 
3,200 / 








1.852 









12,729 


0.15 


3,500 


0.758 


0.20 


0.099 


2.101 


12,730 


0.11 


2,800 


0.756 


0.20 


0.111 


2.125 


12,731 ) 
12,732/ 


0.15) 
0.13/ 


3,000) 
3,100/ 


0.269 


0.30 


0.084 


1.184 


12.733 1 

12.734 r 


0.17) 
0.15/ 


3,500) 

3,200/ 









1.800 









12,752 


0.14 


2,500 


0.631 


0.43 


0.092 


} 2.453 


12,753 


17 


2,500 


(These 


bars had 


fins. 


12,759) 
12,760/ 


0.10) 
0.10/ 


4,000 \ 
4,000 J 


(Semi-steel. ) 
0.382 


1 0.16 


0.170 


1.462 


12,780 ) 
12,781/ 


0.09) 
0.11/ 


2,700) 
3,200/ 


0.716 


0.46 


0.047 


2.468 


12,800) 
12,801 / 


0.13) 
0.13/ 


2,800) 
2,800/ 


0.690 


0.48 


0.048 


2.695 


12,838) 
12,839 / 


0.15) 
0.15 r 


3,700) 
3,000 i 


0.413 


0.36 


0.089 


1.730 


12,840) 
12,841 / 


0.14) 
0.16/ 


3,100) 
3,800/ 






0.094 


1.645 






12,863 \ 
12,864/ 
12,913) 
12,914 / 


0.10) 

o.io; 


3,100) 
3,100/ 


0.723 


0.30 


0.136 


2.275 


0.12) 
0.13/ 


3,300) 
3,300/ 


0.663 


0.32 


0.129 


1.683 


12,915) 
12,916/ 


0.13) 
0.08/ 


?'^^]- 








1.749 


2,900 i 




1 



The results bracketed together signify that the iron was from the same day's cast— some- 
times out of the same ladle, and sometimes not. 



6 



STANDARD SPECIFICATIONS FOR GRAY-IRON CASTINGS. 



Table II. — Results Obtained from Tests Made with 1-in. Square 

Bars. 



No. of 
Specimen. 


Cast No. 


Strength. 


Phospho- 
rus. 


Manga- 
nese. 


Sulphur. 


Silicon. 






Pounds Per 
Sq. In. 


Per Cent. 


Per Cent. 


Per Cent. 


Per Cent. 


12,006 


2 


2,700 


0.765 


0.36 


0.072 


3.305 


12,011 


2 


2,700 


0.605 


0.24 


0.105 


2.718 


12,027 


11/28 


2,800 


0.551 


0.30 


0.118 


1.673 


12,048 


11/20 


3,000 


0.779 


0.46 


0.095 


2.251 


12,065 


11/27 


3,300 


0.722 


0.36 




1.951 


12,079 


113 


2,300 


0.595 


0.56 


"o'.oss"" 


2.016 


12,118 


2 


3,000 


0.580 


0.16 


0.081 


2.769 


12,157 \ 

12,158/ 


206 \ 

207/ 


3,000 \ 
3,000/ 


0.656 \ 
0.651/ 


0.68 \ 
0.36/ 


0.082 \ 
0.115/ 


r 1.894 
\ 1.866 


12,170 


12/10 


2,300 


0.670 


0.88 


0.074 


2.947 


32,1981 


12/5 1 


2,600 ) 








( 1.434 


12,200 [ 


12/8 I 


2,700 ■ 


0.535 


0.32 


0.110 


\ 1.640 


12,2023 


12/10 j 


2,800 J 








(1.419 


12,376 


12/19 


2,400 


0.644 


0.70 


0.097 


3.158 


12.420 \ 

12.421 / 


214 \ 
215/ 


3,000 \ 
2,500/ 


0.626 \ 
0.614/ 


0.38\ 

0.38/ 


0.085 \ 
0.091/ 


/ 2.031 
12.007 


12,427 


2 


2,500 


0.577 


0.24 


0.087 


2.797 


12,761 
12,762 




2,800 
3,000 


Deflectio Ti in 1 9 in. 


0.13 in. 







-*--' ^^ ■*-*■ ^-' V/ 1/ A V/ 

Deflectio 


n in 12 in., 


0.13 in. 






i 



trolled by the machining-properties of the iron. It is my opin- 
ion that a drilling-test would be the best safeguard against a 
too hard iron. As not enough data exist at present to make pro- 
per commercial limits, this matter is one that should be thor- 
oughly investigated. 

A minimum limit for deflection has been placed in the spec- 
ifications to guard against a strong but brittle iron. Such 
iron is not often met, but nevertheless it is a factor and should 
be guarded against. Some of the tests given show a lower 
deflection, but most of them were due to the fact that the bars 
were cast with a sectional mold, the attached fins being subse- 
quently ground ofi*; other low deflections were due to acciden- 
tal defects, and in one set the directions for casting had not 
been followed and the bars had been roughly ground which 
removed the skin in spots. 

The normal specimens cast as directed were better than the 
standard demanded and were as good as that warranted by the 
chemical composition. 

Tensile Strength Test. 
Nothing new is oflfered in this particular. The strength 
limits correspond to the ordinary demands so far as made of 



STANDARD SPECIFICATIONS FOR GRAY-IRON CASTINGS. 7 

the present trade. A uniform gripping-device should be 
adopted as far as possible for the reason that the grip is of 
vital importance in testing cast-iron for tensile strength. 

Definition. 
The classification made is approximate and will naturally be 
supplemented by buyers who will specify that a given casting 
must conform to the specifications applying to one of the 
grades. This will remove all uncertainty as to w^hich class may 
be meant. 

Arbitration Bar. 

It was the first choice of the committee that a 1.5 in. -bar 
might be used, in fact, a bar that would be as large as possible 
in order to be free from all chilling influences and defects re- 
sulting from sudden cooling; in short, a less sensitive bar. It 
was seen that such a bar w^ould break at too great a strength 
and be beyond the limits of the majority of testing machines 
now in use in foundries. A diameter of 1.25 in. was therefore 
adopted as being satisfactory, all things considered. 

The question arose of having one standard size of test-bar as 
•compared with having several, in order to make an approxi- 
mate comparison of thicknesses with the castings under inspec- 
tion and thus duplicate the actual cooling conditions. This is 
not possible, because any separate bar must cool more or less 
slowdy than the casting, and any coupon-cast as a part of the 
•casting must be machined before testing. A test of this kind 
made without the skin does not represent the actual casting, 
nor can like conditions be duplicated at will in this way. 

By having a standard bar it is perfectly possible to estimate 
the strength of any other bar or casting, just as in the case of 
the steel maker who rolls a standard test-bar, say 2J by | in. 
in section from a small 6 in. square test ingot, and from the re- 
sults obtained is able to foretell the strength of the same steel 
rolled into a f-in. rod, a 0.5-in. angle-iron, or a 1.25-in. plate. It 
is all a question of heat treatment and speed of cooling, and in 
this respect cast-iron is similar to steel. Cooling conditions 
follow very definite laws well recognized by the average foun- 
der without his analyzing the reasons. Any grade or quality 
of cast-iron may be purchased with the arbitration test-bar as 
specified, as well as by a dozen dififerent sizes of test-bars. It 



8 STANDARD SPECIFICATIONS FOR GRAY-IRON CASTINGS. 

is a matter of comparison at the best, and one standard is- 
enough. 

As a study it would be interesting to cut out specimens from, 
all sizes of castings as far as possible, and the results would 
form a basis for future comparison, but as a commercial custom 
this suggestion is practically and commercially out of the ques- 
tion. 

The importance of the tensile test has been minimized 
because of the great difficulty of making true tensile tests.. 
Abnormal strains are sure to creep in except in the most care- 
fully constructed machines operated by the most skilled ob- 
servers. 

The transverse test is within the reach of all and, in fact,, 
corresponds with the conditions of actual use much closer than 
does the tensile test, and no serious abnormal strains are pos- 
sible with the ordinary testing machine. 

The occasion is likely to arise in which the tensile test will 
be advisable, to meet which the provision noted in the specifi- 
cations is inserted. The shape of the specimen resembles quite 
closely the one in use by the Government, but it has been 
modified to meet the needs of the piece from which it is to be- 
cut, as well as of other practical considerations. It has been 
made as short as possible to eliminate the chance of including 
fiaws, and it has been lengthened as compared with the Gov- 
ernment specimen, which is likely to give abnormally high, 
results. 

Conditions of Casting. 

Probably the most important source of varying results in 
cast-iron tests has been the uncertain conditions surrounding 
molding and casting. There never has been any uniformity in 
this respect, yet it is a well-known fact that cast-iron is very 
much infiuenced by various chilling effects, and is extremely 
sensitive to all heat- variations. Some foundrymen have made 
the molds in sand that is quite moist and others in sand that is 
very dry. Some have knocked the test-bar out of the mold as 
quickly as it became cool enough to stand it. Some have cast 
the bar on end, some flat, and some inclined, the variations 
being nearly as many as the number of founders. It has there- 
fore been provided that the mold shall be dry and cool before 
the bar is cast and the other conditions shall be observed which 
will tend to produce uniform castings. 



STANDARD SPECIFICATIONS FOR (JRAY-IRON CASTINGS. »• 

I note that by some error a provision to prevent the Icnont 
=ng out of the test-bar from the mold has bLrom tS Tht 
prov,s,on was contained in the instructions sent for casting i 
bar tested and I doubt that all the conditions were observed 
forif oneinfnngement in the matter of casting in a parted mold 

ZZt r'^'K ^'"^ "^^^ ^*^^^^- '^^-^ -lifferenceru ' 
doubtedly account for some of the abnormal variations. 

Some of the bars submitted for the test were cast in a parted 
mold, producmg fins of greater or less thickness, which were 
chipped or ground off. The result of this condition was that le I 
deflection resulted, even though the fins were placed at the 
neutral axis of the test specimen. 
_ The provision stating that the test-bars should not be treated 

portant The facing of the mold has been particularly speci- 
fied, so that the test-bar shall strip from the mold in fairly |ood 
shape and be ready for the test. ' ^ 

The objection has been made that the bars could not be 
made sufficiently uniform in diameter_an effect which is Ir 
or less true when the iron is cast in a green sand mold ; but Jh 
the stated casting conditions which prohibit the rapp ng of the 
pattern and with the use of a dry mold and a gLen facint 
ns objection has almost disappeared and has bfcome o I' 
tremely small importance. Measurements made of 20 bars 
show a maxmium variation of but 0.039 in. in an avera<.e 
diameter at the break of 1.236 inches. ^ 

Table in.-Measuremmts of Arbitration Test-Bars at the Point 

of Rupture. 



No. of 
Spec- 
imen. 



Diameter 

in 
Inches. 



1.240 
1.241 



No. of 
Spec- 
imen. 



1.231 


10 


1.221 


11 


1.233 


12 


1.244 


13 


1.286 


14 



Diameter in Inches, 



No. of 
Spec- 
imen. 



Diameter in Inches. 



1.246 

1.273 

1.231 
1.234 
1.242 

1.220 This bar was 

ground smooth. 
1.233 



15 

16 

17 
18 
19 



1.180 This bar cast 

with fins. 
1.236 Rounded off 

by grindinfir. 
1.243 ^ 

1.245 
1.259 



20 i 1.238 



It is interesting to note th^T^hT^^ar ca^^^wTfi^T^t 



10 STANDARD SPECIFICATIONS FOR GRAY-IRON CASTINGS. 

is, in a parted mold, was the most abnormal of the lot, which 
ought to be considered a most excellent endorsement of the 
proposed method of molding. 

The question of the character of the supports to be used 
during the test has been raised, but it is believed that little 
need be feared on this account, as the testing machines in 
common use are safe in this matter. In the tests given in 
Tables I. and 11. , the point of contact where the load was ap- 
plied has a radius of about 0.25 in., but no mark is left on the 
casting, and it is doubtful if this would cause any diiference 
unless the edge were exceedingly sharp, or was a flat surface. 
The tw^o end-bearings used were flat surfaces intended to rotate 
on a round bearing. The rotation was not perceptible. Either 
bearings of this kind, or blunt knife edges, in all probability, 
would answer equally well. 

Speed of Testing. 

The time limit of the test has been placed to meet ordinary 
practice, as near as can be ascertained. In all events it is within 
reason, and as long as the practice is made uniform by diflfer- 
ent observers, it is of comparative small moment. 

Samples for Chemical Analysis. 

This simple provision has been made with the understand- 
ing that the boring shall be taken after removing all of the 
surface matter. In case graphitic carbon enters into the case, 
the sample should be taken across the entire face or cross-sec- 
tion of the bar and thoroughly mixed, — a procedure which is 
necessary because of the diflTerence in graphitic carbon exist- 
ing between the exterior and interior metal of a specimen of 
the size in question. 

I recognized that these specifications for gray-iron castings 
are not ideal from every standpoint, nor is it possible that any 
commercial ones may be. Theory must yield to practice all 
along the line, and every engineer or manager discovers this 
fact very early in his connection with manufacturing condi- 
tions. 

The Committee believes that by means of these specifica- 
tions the purchaser of gray-iron castings will be able to obtain 
a more uniform and reliable product. It is also certain that 



STANDARD SPECIFICATIONS FOR GRAY-IRON CASTINGS. 11 

there will be correspondiiigl}^ less friction, because an order 
for iron-castings will be definite as to quality, and if the foun- 
dry makes them to fill the specifications, there can be no dis- 
pute as to the quality of the iron furnished because some ma- 
chinist thinks it machines hard or thinks it looks weak. 



Note by the Secretary. — Comments or criticisms upon all 
papers, whether private corrections of typographical or other 
errors or communications for publication as '' Discussions," or 
independent papers on the same or a related subject, are earn- 
estly invited. 



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